Homoiothermy

Among living creatures that exist today, birds and mammals are homoiothermic (the only exception is naked mole rats). In addition, on May 15, 2015, the first fully warm-blooded fish was discovered by scientists from the US National Oceanic and Atmospheric Administration. The question of whether pterosaurs and dinosaurs were warm-blooded animals is also debatable, although recently researchers are increasingly inclined towards warm-bloodedness, and disputes are already about which of the species were warm-blooded and which were not. It is also not entirely clear what kind of endothermy dinosaurs had, but the available evidence suggests that large dinosaurs had at least inertial homoiothermy.

Types of homoiothermy

True homoiothermy occurs when a living being has a sufficient metabolic rate to maintain its body temperature at a constant level through self-production of energy from the food it consumes. Modern birds and mammals are truly homoiothermal creatures. In addition to sufficient energy capabilities, they also have various mechanisms designed to retain heat (feathers, wool, subcutaneous layer of adipose tissue) and to protect against overheating at high ambient temperatures (sweating). The disadvantage of this mechanism is that a lot of energy is needed to maintain body temperature, and, accordingly, the need for food is higher than in any other case.

Inertial homoiothermy is the maintenance of a constant body temperature due to large size and large body weight, as well as specific behavior (for example, bask in the sun, cool in water). The effectiveness of the mechanism of inertial endothermy depends primarily on the ratio of heat capacity (simplified, mass) and the average heat flux through the body surface (simplified, body area), so this mechanism can be clearly observed only in large species. An inertial-homoiothermal being slowly heats up during periods of rising temperature, and during periods of cooling it slowly cools down, that is, due to the large heat capacity, fluctuations in body temperature are smoothed out.The disadvantage of inertial homeothermy is that it is possible only in a certain type of climate - when the average ambient temperature corresponds to the desired body temperature and there are no long periods of severe cooling or warming. Of the advantages, a small need for food with a fairly high level of activity should be highlighted. A typical example of inertial homeothermy is the crocodile. The skin of a crocodile is covered with rectangular horny shields, which are arranged in regular rows on the back and abdomen, under them in the dorsal and less often in the abdominal part osteoderms develop, forming a shell. Osteoderms in the daytime accumulate heat coming along with sunlight. Due to this, the body temperature of a large crocodile during the day can fluctuate within only one or two degrees. Along with crocodiles, a state close to inertial homoiothermy can be observed in the largest land and sea turtles, as well as Komodo dragons, large pythons and boas.

Homoiothermic animals regulate body temperature regardless of environmental conditions. The mechanism is energy-consuming, but it allows organs and systems to always function with comfortable heating.

In nature, there are also poikilotherms. Homoiothermic animals are considered superior to them in terms of development, evolution. Poikilotherms heat up and cool down together with the environment. Some jumps in temperature are ruining. Others slow down the processes of life, falling into hibernation.

Ground frogs, for example, hibernate in the ground in a state of suspended animation. In addition to amphibians, poikilothermic creatures include reptiles, fish, protozoa, and invertebrates. Hence, mammals and birds are homoiothermal.

Evolutionary mechanisms of adaptation of homoiothermic animals

Since warm-blooded animals do not depend on their environment to maintain their body temperature, they can live in both hot and cold regions of the world. They have various adaptations to keep warm, including thick coats, feathers in birds, or blubber in marine mammals.

There are also various behavioral responses, including chills, migration, or hibernation during the cold season. Some birds migrate thousands of kilometers to warmer regions. There are also many small warm-blooded birds and mammals known to hibernate.

Sweat glands are used to lower body temperature; in primates they are present throughout the body, while in cats and dogs the glands are found only on the legs. Shortness of breath is another mechanism for heat loss.